Conductive traces or paths within an interconnect scheme, such as a circuit board or a multi-chip module, may be formed with an ink having conductive particles dispersed within a carrier fluid or binder. Although the carrier fluid may be non-conductive, electrical current is able to flow through the ink due to physical contact between the particles, which form a network of conductive paths through the ink.
Because interconnect schemes may be difficult and/or expensive to design and produce, and may contain sensitive information (e.g., proprietary information), owners and developers of interconnect schemes may wish to keep the schemes secret, prevent reverse engineering, and/or prevent tampering. Available techniques for protecting interconnect schemes include: detecting tamper or intrusion and taking countermeasures; adding dummy chips and extraneous conductive traces; applying obscuring or masking layers (e.g., to block or scatter light, x-rays, or sounds); implementing deciphering keys that are destroyed upon tampering; and employing a Physically Unclonable Function (PUF). Unfortunately, these techniques are not always effective. For example, obscuring or masking layers may be removed by sectioning or grinding. In addition, none of the other techniques identified above prevent an interconnect scheme from being identified using conventional methods, such as optical inspection, acoustic inspection, and x-ray inspection.
Accordingly, there is a need for materials and methods for producing interconnect schemes that are tamper-resistant and difficult to identify and reverse engineer. In particular, methods and materials are sought for producing interconnect schemes that cannot be identified using conventional detection methods.